Answer:
x = 10
Step-by-step explanation:
Divide both sides by 2.
(2x) / 2 = 20 / 2
x = 10
What aboout it? please clarify.
Answer:
100
Step-by-step explanation:

This can be turned into:
(if we add the numbers inside the brackets)
Following PEDMAS, this becomes:
which equals 
∴
Answer: Todd used 27 black tiles.
Step-by-step explanation:
Let x represent the number of black tiles that Todd used.
Todd uses 21 white tiles & some black tiles to make a mosaic. This means that the total number of white and black tiles that Todd used is 21 + x
Each tile has an area of 3 square centimeters. This means that the total area covered by the white tiles is
21 × 3 = 63 square centimeters
Also, the total area covered by the black tiles is
3 × x = 3x square centimeters
The mosaic has a total area of 144 square centimeters. This means that
3x + 63 = 144
3x = 144 - 63
3x = 81
x = 81/3 = 27